sometimes seen within the C3st. When treated with H2SO4 , cysts are easily broken up under the cover glass. Fruiting bodies are composed of climips of cysts. The fruit- ing bodies are ellipsoidal or pear-shaped, 40 to 55 by 110 to 160 microns, reddish brown; they are covered with a slime mem- brane (flakes of dried slime). Each is com- posed of 12 to 40 cysts which become poly- gonal from pressure. The cysts are some- times arranged in chains. Resting cells: 0.7 to 0.8 by 2.2 to 3.5 mi- crons. Vegetative colony: Cysts germinate on filter paper producing vegetative colonies. Colonies large, orange, moist, increasing in size. The older colonies have orange margins while the center is dark brown, correspond- ing to the color of the fruiting bodies. Often show several concentric rings. Physiology: Rods cover cellulose fibers, partially or completelj^ destroying them. Paper becomes transparent. Optimum temperature, between 18° and 22° C. Very slow growth at 30° C. Grows only on cellulose, not in ordinary media. Aerobic. Source: Isolated from soil. Illustrations: Imsenecki and Solntzeva {ibid., Table II, 2, Figs. 1-5). 5a. Polyangium cellulosum var. ferru- gineum Mishustin, 1938. (Microbiologia, 7, 1938, 427.) fer.ru. gi'ne.um. L. adj. ferrugineus of the color of iron rust. Vegetative cells: Long, flexible cells, 0.8 to 1.2 by 3.0 to 5.0 microns. Become short- ened and highly refractile during fruiting- body formation. Fruiting bodj-: Composed of numerous cysts having definite wall. Mass of rods has a yellowish tinge, and the cysts are colored reddish yellow. Color probably confined to the cyst walls. Cysts round or egg-shaped, or may be angular due to pressure. Each cyst contains numerous shortened rods. Cysts usually 12 to 40 microns in diameter. Numerous cysts grouped into fruiting bodies having bright red or drabbish red color when ripe. Form of fruiting body variable: most commonly rounded, ellipsoidal or biscuit- shaped, sometimes sausage-shaped. Cysts confined by an orange-colored slime mem- brane or envelope. No cystophore present. Fruiting bodies not easily broken up. Vary in size from 80 to 240 microns. Vegetative colony: On silica gel with cel- lulose, at first pale pink. After six days fruiting bodies of red color appear together with free cysts and many non-encysted shortened rods. Fruiting bodies numerous at center of colony and later form in con- centric rings around center. Margin of col- ony composed of vegetative cells; periphery pink. Mature colonies 2 to 5 cm in diameter, bright red, becoming drabbish red; pigmen- tation appears to be confined to limited areas. Surface dull, moist. Margin not defi- nite. Physiology: The cellulose at the center of the colony is completely destroyed, whereas that under the remainder of the colony is not entirely broken down. The author considers this a color variant of Polyangium cellulosum Imsenecki and Solntzeva. Source: Isolated from the black soils of Eastern European Russia. Habitat: Soil. Decomposes cellulose. 5b. Polyangium cellulosum var. fuscxim Mishustin, 1938. (Microbiologia, 7, 1938, 427.) fus'cum. L. adj. fuscus dark, tawny. Vegetative cells: Identical with those of Polyangium cellulosum var. ferrugineum. Fruiting body: Composed of individual cysts, each with a separate cyst wall, and held together by a common slime membrane or envelope. Shortened, rod-shaped spores enclosed within the cyst walls. Cysts form- ing outside the large walls. Cysts forming outside the large masses usually rounded; those within often polygonal or angular. Cysts 5 to 24 microns long, ellipsoidal or egg-shaped. Encysted cells give cysts gran- ular appearance. Ripe cj^sts brown to light brown in color; immature, yellow to pink. Fruiting bodies pinkish yellow when young, becoming brown when ripened. Considera- ble variation in form: round, ellipsoidal or sausage-shaped, and from 50 to 80 microns up to several hundred microns. Outer slime envelope often indistinct; no dried slime noticeable between the cysts.
